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A study of the causal relationship between the emergence of a twisted magnetic flux rope and a small Hα two-ribbon flare
Brooks, D. H.; Kurokawa, H.; Berger, T. E. +2 more
We present results from an analysis of a small two-ribbon flare which occurred above emerging flux in solar active region NOAA 8218 on 1998, May 13th and which was observed by the Swedish Vacuum Solar Telescope (SVST) on the island of La Palma, Spain. The relatively simple magnetic morphology and small size of the flare together with the high qual…
The HST survey of the B2 sample of radio galaxies: Detection of two optical jets
Bondi, M.; Capetti, A.; Morganti, R. +5 more
We present HST observations of previously undetected optical jets in the low-luminosity radio galaxies B2 0755+37 and B2 1553+24. We show that there is accurate spatial coincidence between optical and radio emission, implying that the former is likely to be synchrotron radiation. The physical properties of the jets are similar to those known previ…
Evolution of the galactic cosmic ray electron to proton ratio: Ulysses COSPIN/KET observations
Kunow, H.; Ferreira, S. E. S.; Potgieter, M. S. +3 more
The Ulysses orbit provides a unique opportunity to study the propagation of cosmic rays in a wide range of heliographic latitudes and during different solar activity and polarity in the inner heliosphere. Around July 2000 the solar magnetic field reversed its global polarity. In late 2000, the electron to proton ratio at the rigidities of 1.2 GV a…
The RR Lyrae star period - K-band luminosity relation of the globular cluster M 3
Butler, D. J.
That the RR Lyrae star period - K-band luminosity relation is a promising tool as a distance indicator in the Milky Way and Local Group of galaxies is apparent on observational and theoretical grounds in the literature. Less clear is the sensitivity of the relation, and consequently the physics of horizontal branch stars, to differences in stellar…
Dependence of UV radiance of the quiet Sun on the solar cycle: Surface magnetic fields as the cause
Solanki, S. K.; Pauluhn, A.
The quiet-Sun UV radiance depends on the solar cycle, as shown by data collected by the SUMER spectrograph on the Solar and Heliospheric Observatory (SOHO). The cause of this dependence is still unclear. Here the hypothesis is tested for the He I 584 Å line that these variations are due to changes in the magnetic network. The quiet-Sun variability…
On the nature of extended EUV filaments
Heinzel, P.; Anzer, U.
This paper describes the properties of extended EUV filaments and the theoretical modelling of them. We summarise the general aspects of the depression of EUV-line emission and give an interpretation of recent filament observations in transition-region and coronal lines. The EUV filament was found to be located relatively high in the corona (at le…
ISOCAM-CVF imaging of M 16
Pilbratt, G. L.; White, Glenn J.; Urquhart, J. S. +1 more
We present ISOCAM observations (5-17 mu m) of the HST M 16 field, including the striking elephant trunk structures. The spectroscopic data have been obtained using the ISOCAM-CVF low-resolution mode, having a spectral resolution of ~ 40 (lambda /Delta lambda ) and a pixel size of 6''. The spectra show a combination of Unidentified Infra…
Past and recent observations of the solar upper atmosphere at vacuum-ultraviolet wavelengths
Wilhelm, Klaus
Our understanding of the high-temperature solar atmosphere is to a large extent based on spectroscopic observations of emission lines and continuum radiation in the vacuum-ultraviolet (VUV) wavelength range of the electromagnetic spectrum. In addition, important contributions stem from soft X-ray measurements. The VUV radiation is produced by tran…
Effect of anisotropic velocity distribution on the linear polarization of coronal lines. Does the ion cyclotron exist in the inner corona?
Solanki, S. K.; Raouafi, N. -E.
The effect of an anisotropic velocity field distribution of scattering ions on the polarization parameters of a spectral line emitted by resonance scattering is considered. The anisotropy of the velocity field distribution can be interpreted in terms of the ion-cyclotron effect that is believed to influence some heavy ions in the solar corona. We …
Upgrades to the Flagstaff Astrometric Scanning Transit Telescope: A Fully Automated Telescope for Astrometry
Harris, Hugh C.; Vrba, Frederick J.; Munn, Jeffrey A. +13 more
The Flagstaff Astrometric Scanning Transit Telescope (FASTT) is a fully automated telescope that takes about 41,000 CCD frames of data a year for various research projects. All aspects of the telescope's operation have been automated (e.g., target selection, observing, reduction of data, and collation of results), and manpower needs are now under …